Wastewater Treatment

What is DEWATS?

Decentralized Wastewater Treatment System (DEWATS) can be described as a low maintenance treatment system, treating small volumes of wastewater for reuse or discharge within National Standards. DEWATS generally treats domestic wastewater originating from individual or groups of dwellings, businesses or institutions that are located in close proximity to each other and the DEWATS site. Unlike conventional wastewater treatment plants, DEWATS promotes technologies that use natural processes and are simples in operation and maintenance. In DEWATS, natural treatment processes are achieved through methods that make use of physical principles combined with biological activities of microorganisms. Bacteria colonies in the treatment devices are generated from microbial populations that occur naturally in the wastewater.

 

The size of a DEWATS can range from individual onsite systems that serve one household or institution; to shared facilities that serve up to ten households or public/community facilities serving up to 2000 households. Since the distance between the point of origin and treatment of wastewater is small, elaborate collection systems and pumping equipment is avoided thereby reducing costs. This also allows for easier reuse of treated water which again makes the whole system cost efficient.

typical-DEWATS

Typical DEWATS combine the following technical treatment steps in a modular manner.

(1) Primary Treatment

  • The primary treatment phase retains all settable solids and allow only dissolved solids to discharge.
  • In settler, sedimentation tank, septic tank or biogas settler.
  • Another type of primary treatment is sedimentation tank for collection and use of biogas generated from decomposition of settled organic particles.

 

(2) Secondary Treatment

  • Suspended and dissolved solids in the wastewater undergo anaerobic degradation due to contact with an active sludge blanket on the bottom of each chamber.

 

(3) Tertiary Treatment

  • It is the secondary and/or tertiary treatment phase and cleans the wastewater by biological conversion, physical filtration and chemical adsorption.

 

(4) Sludge Treatment

  • Sludge generated from primary and secondary treatment units can be dried applying on sand beds, which is also called sludge drying beds. De-sludging intervals can be set to coincide with the dry season in order speed up the drying process.
combine

EXISTING DEWATS IN NEPAL

S.N. Location Type Year Built
1 Dhulikhel Hospital Hospital 1997
2 Dallu, Private House Domestic 1998
3 Kathmandu University Institutional 2001
4 ENPHO Laboratory Institutional 2002
5 Malpi International School Institutional 2002
6 Sushma Koirala Memorial Plastic &Reconstructive Surgery Hospital Hospital  2002
7 Kapan Monastry Institutional 2002
8 Private House at Dallu Domestic 2002
9 Septage Treatment, Pokhara Community 2003
10 Shuvatara School, Lamatar Institutional 2004
11 Surya Tobacco Industrial 2005
12 Private House, Bishal Nagar Domestic 2005
13 Sunga, Thimi Municipal 2006
14 Kirtipur Housing Community Community 2006
15 Kusunti Housing Community 2007
16 Ilam Polyclinic Hospital 2007
17 Sano Khokana Community Community 2008
18 Srikhandapur Community 2008
19 Monastry in Pharping, Dakshinkali Institutional 2009
20 Private House at Kirtipur Domestic 2010
21 Namo Bhudha Resort 2012
22 Thakuri Gaun Sub System 2009
23 Pipal Bot Sub System 2009
24 Srikhandapur Community Wastewater Treatment Plant 2008
25 Nala Community Wastewater Treatment Plant 2012
26 Panauti Wastewater Treatment Plant 2009
27 Chandeshwori Wastewater Treatment Plant 2009
28 Budole Wastewater Treatment Plant 2009
29 Landfill Site Wastewater Treatment Plant 2009
30 Gokarna Wastewater Treatment Plant(I) 2012
31 Gokarna Wastewater Treatment Plant(II) 2014
32 Gokarna Wastewater Treatment Plant (III) 2016
33 Kapan Monastry 2002
34 Satya Sai Sikshya Sadan 2014
35 School at Dallu 2010
36 Central Horticulture Center 2011
37 Neydo Monastry 2009
38 Kusunti Housing 2007
39 ICIMOD 2010
40 Ama Ghar 2010
41 Suvatara School 2004
42 Park Village Water Front Resort 2011
43 Hetauda Wastewater Treatment Kara Sub System 2009
44 Hetauda Waste Treatment Rapti II Sub System 2009
45 Hetauda Wastewater Treatment Rapti II Sub System 2009
46 Hetauda Industrial Wastewater Treatment Plant 2003
47 Bharatpur Wastewater Treatment Plant (C1) 2009
48 Bharatpur Wastewater Treatment Plant (C2) 2009
49 Surya Nepal Pvt. Limited (Staff Housing) 2005
50 Lumbini Medical College and Teaching Hospital
51 Sidhartha Childern and Women Hospital (AMDA)
52 Middle Marshyangdi Hydro Electric Power Station (Staff Quarter)
53 Teku Septage Treatment Plant 1998
54 Dallu Private House (II) 2002
55 Septage Treatment, Pokhara 2003
56 Bishal Nagar 2005
57 Lubhoo FSTP 2016
58 Kupondole 2011
59 Hope Center Nepal 2016
60 Disable Children Home 2016
61 Basundhara I 2013
62 Basundhara II 2014
63 Imadole 2009
64 Chahuni 2011
65 kimdole 2016
66 ECCA
67 Kupondole 2010
68 Bottlers Nepal Limited, Balaju 2001
69 Bottlers Nepal (Terai) Limited, Bharatpur 2005
70 Western Regional Hospital 2013
71 Chandra Ban Eco Resort 2012
72 Lumanti Support Group for Shelter 2016
73 Birat Eye Hospital
74 Illam Polyclinic